1. Field of the Invention
The present invention relates to a production process of a color filter suitable for use in color liquid crystal display devices used in color televisions, car televisions, personal computers, etc., and inks suitable for use in the production of the color filter, and particularly to a production process of a color filter for liquid crystal display device making good use of an ink-jet recording technique and inks suitable for use in the production of such a color filter.
2. Related Background Art
With the advancement of personal computers, particularly, portable personal computers in recent years, the demand for liquid crystal display devices, particularly, color liquid crystal display devices tends to increase. It is however necessary to reduce the cost of the color liquid crystal display devices for further spreading them. There is an increasing demand for reduction in the cost of color filters particularly given much weight from the viewpoint of the cost.
Various methods have heretofore been attempted for meeting the above demand while satisfying properties required of the color filters. However, no method satisfying all the required properties is yet established. The individual methods will hereinafter be described.
The first method oftenest used is a dyeing process. In the dyeing process, a water-soluble polymeric material, which is a material to be dyed, is first applied to a glass base, and the coating film thus formed is patterned in the desired form by a photolithographic process. Thereafter, the base on which the coating film has been patterned is immersed in a dye bath to obtain a colored pattern. This process is repeatedly performed three times to produce a color filter composed of colored patterns of red (R), green (G) and blue (B).
As another illustration of this dyeing process, Japanese Patent Application Laid-Open No. 5-288913 describes a production process of a color filter composed of three colored patterns of R, G and B, wherein a photosensitive layer is provided on a base to expose on the desired pattern, unexposed portions of the photosensitive layer are dyed, and this process is repeatedly performed three times.
The second method is a pigment dispersing process which has been replacing the dyeing process in recent years. In this process, a layer of a photosensitive resin in which a pigment has been dispersed is first formed on a base and then subjected to patterning, thereby obtaining a pattern of a single color. This process is repeatedly performed three times, thereby producing a color filter composed of colored patterns of R, G and B.
As the third method, there is an electrodeposition process. In this process, a transparent electrode is first patterned on a base. The base is then immersed in an electrodeposition coating fluid containing a pigment, resin, electrolytic solution and the like to electrically deposit the first color. This process is repeatedly performed three times, thereby forming a color filter layer composed of colored patterns of R, G and B. Finally, this color filter layer is calcined to produce a color filter.
The fourth method is a process in which pigments are separately dispersed in a thermosetting resin, the resultant thermosetting resin dispersions of R, G and B colors are separately applied to a base by repeating printing three times, and the resin portions thus applied are then thermoset to form a colored layer.
It is general to form a protective layer on the colored layer in each process.
The need of repeating the same process three times to form the three colored patterns of R, G and B is common to these processes. Therefore, the production cost is necessarily increased. There is also offered a problem that a yield is reduced as the number of processes increases. Further, in the electrodeposition process, formable patterns are limited. It is hence difficult to apply this process to a TFT color liquid crystal display device in the existing technique. Further, the printing process is poor in resolution, and so fine-pitch patterns are difficult to form.
In order to supply these drawbacks, Japanese Patent Application Laid-Open Nos. 59-75205, 63-235901 and 1-217320 each have proposed a process for producing a color filter using an ink-jet printing system. However, these processes are not yet satisfactory.
Japanese Patent Application Laid-Open No. 5-224007 describes inclusion of a melamine compound in inks. However, these inks involve a drawback from the viewpoint of ejectability from an ink-jet head.